History

Creatine was first identified in 1832 when Michel Eugène Chevreul isolated it from the basified water-extract of skeletal muscle. He later named the crystallized precipitate after the Greek word for meat, κρέας (kreas). In 1928, creatine was shown to exist in equilibrium with creatinine.[3] Studies in the 1920s showed that consumption of large amounts of creatine did not result in its excretion. This result pointed to the ability of the body to store creatine, which in turn suggested its use as a dietary supplement.[4]

The discovery of phosphocreatine[7][8] was reported in 1927.[9][10][8] In the 1960’s, creatine kinase (CK) was shown to phosphorylate ADP using phosphocreatine (PCr) to generate ATP. It follows that ATP, not PCr is directly consumed in muscle contraction. CK uses creatine to “buffer” the ATP/ADP ratio.[11]

While creatine’s influence on physical performance has been well documented since the early twentieth century, it came into public view following the 1992 Olympics in Barcelona. An August 7, 1992 article in The Times reported that Linford Christie, the gold medal winner at 100 meters, had used creatine before the Olympics. An article in Bodybuilding Monthly named Sally Gunnell, who was the gold medalist in the 400-meter hurdles, as another creatine user. In addition, The Times also noted that 100 meter hurdler Colin Jackson began taking creatine before the Olympics.[12][13]

At the time, low-potency creatine supplements were available in Britain, but creatine supplements designed for strength enhancement were not commercially available until 1993 when a company called Experimental and Applied Sciences (EAS) introduced the compound to the sports nutrition market under the name Phosphagen.[14] Research performed thereafter demonstrated that the consumption of high glycemic carbohydrates in conjunction with creatine increases creatine muscle stores.[15]

The cyclic derivative creatinine exists in equilibrium with its tautomer and with creatine.

Biosynthesis

Creatine synthesis primarily occurs in the liver and kidneys.[2][16] On average, it is produced endogenously at an estimated rate of about 8.3 mmol or 1 gram per day in young adults.[16][17] Creatine is also obtained through the diet at a rate of about 1 gram per day from an omnivorous diet.[16][18] Most of the human body’s total creatine and phosphocreatine stores are found in skeletal muscle, while the remainder is distributed in the blood, brain, and other tissues.[17][18]

Synthesis primarily takes place in the kidney and liver, with creatine then being transported to the muscles via the blood. The majority of the human body’s total creatine and phosphocreatine stores is located in skeletal muscle, while the remainder is distributed in the blood, brain, and other tissues.[17][18][20] Typically, creatine is produced endogenously at an estimated rate of about 8.3 mmol or 1 gram per day in young adults.[16][17] Creatine is also obtained through the diet at a rate of about 1 gram per day from an omnivorous diet.[17][18] Some small studies suggest that total muscle creatine is significantly lower in vegetarians than non-vegetarians, as expected since foods of animal origin are the primary source of creatine. However, subjects happened to show the same levels after using supplements.[21]

Phosphocreatine system

Creatine, which is synthesized in the liver and kidneys, is transported through the blood and taken up by tissues with high energy demands, such as the brain and skeletal muscle, through an active transport system. The concentration of ATP in skeletal muscle is usually 2–5 mM, which would result in a muscle contraction of only a few seconds.[22] During times of increased energy demands, the phosphagen (or ATP/PCr) system rapidly resynthesizes ATP from ADP with the use of phosphocreatine (PCr) through a reversible reaction with the enzyme creatine kinase (CK). In skeletal muscle, PCr concentrations may reach 20–35 mM or more. Additionally, in most muscles, the ATP regeneration capacity of CK is very high and is therefore not a limiting factor. Although the cellular concentrations of ATP are small, changes are difficult to detect because ATP is continuously and efficiently replenished from the large pools of PCr and CK.[22] Creatine has the ability to increase muscle stores of PCr, potentially increasing the muscle’s ability to resynthesize ATP from ADP to meet increased energy demands.[23][24][25]

Supplement health effects

Use

Creatine use can increase maximum power and performance in high-intensity anaerobic repetitive work (periods of work and rest) by 5 to 15%.[28][29][30] Creatine has no significant effect on aerobic endurance, though it will increase power during short sessions of high-intensity aerobic exercise.[31][32]

A survey of 21,000 college athletes showed that 14% of athletes take creatine supplements to improve performance.[33] Non-athletes report taking creatine supplements to improve appearance.[33]

Creatine is reported to increase cognitive performance,[34] especially in individuals with inadequate intakes in their diet and is claimed by some sources [35][36] to be a nootropic supplement.

Nutritional supplement

Creatine-monohydrate is suitable for vegetarians and vegans, as the raw materials used for the production of the supplement have no animal origin.[37]

Therapeutic use

According to a clinical study focusing on people with various muscular dystrophies, using a pure form of creatine monohydrate can be beneficial in rehabilitation after injuries and immobilization.[38]

Medical use

A clinical study has shown that the intake of pure, high-quality creatine alone, or in combination with exercise, may reduce and delay age-related muscle atrophy, by improving fat-free body mass, muscle strength and endurance, while simultaneously improving bone density.[39]

People with kidney disease, high blood pressure, or liver disease should not take creatine as a dietary supplement.[45]

One well-documented effect of creatine supplementation is weight gain within the first week of the supplement schedule, likely attributable to greater water retention due to the increased muscle creatine concentrations.[46]

A 2009 systematic review discredited concerns that creatine supplementation could affect hydration status and heat tolerance and lead to muscle cramping and diarrhea.[47][48]

Interactions

Creatine taken with medications that can harm the kidney can increase the risk of kidney damage:[45]

A National Institutes of Health study suggests that caffeine interacts with creatine to increase the rate of progression of Parkinson’s Disease.[49]

Contamination

A 2011 survey of 33 supplements commercially available in Italy found that over 50% of them exceeded the European Food Safety Authority recommendations in at least one contaminant. The most prevalent of these contaminants was creatinine, a breakdown product of creatine also produced by the body.[50] Creatinine was present in higher concentrations than the European Food Safety Authority recommendations in 44% of the samples. About 15% of the samples had detectable levels of dihydro-1,3,5-triazine or a high dicyandiamide concentration. Heavy metals contamination was not found to be a concern, with only minor levels of mercury being detectable. Two studies reviewed in 2007 found no impurities.[44]

Food safety

When creatine is mixed with protein and sugar at high temperatures (above 148 °C), the resulting reaction produces carcinogenic heterocyclic amines (HCAs).[51] Such a reaction happens when grilling or pan-frying meat.[52] Creatine content (as a percentage of crude protein) can be used as an indicator of meat quality.[53]

Chemistry

Creatine is a derivative of the guanidinium cation. A cyclic form of creatine, called creatinine, exists in equilibrium with its tautomer and with creatine. Creatine undergoes phosphorylation, by the action of creatine kinase to give phosphocreatine. The phosphate group is attached to an NH center of the creatine. The P-N bond is highly reactive.

Pharmacokinetics

This graph shows the mean plasma creatine concentration (measured in μmol/L) over an 8-hour period following ingestion of 4.4 grams of creatine in the form of creatine monohydrate (CrM), tri-creatine citrate (CrC), or creatine pyruvate (CrPyr).[54]

Endogenous serum or plasma creatine concentrations in healthy adults are normally in a range of 2–12 mg/L. A single 5 g (5000 mg) oral dose in healthy adults results in a peak plasma creatine level of approximately 120 mg/L at 1–2 hours post-ingestion. Creatine has a fairly short elimination half-life, averaging just less than 3 hours, so to maintain an elevated plasma level it would be necessary to take small oral doses every 3–6 hours throughout the day.
After the “loading dose” period (1–2 weeks, 12–24 g a day), it is no longer necessary to maintain a consistently high serum level of creatine. As with most supplements, each person has their own genetic “preset” amount of creatine they can hold. The rest is eliminated as waste. A typical post-loading dose is 2–5 g daily.[55][56][57]

Creatine supplementation appears to increase the number of myonuclei that satellite cells will ‘donate’ to damaged muscle fibers, which increases the potential for growth of those fibers. This increase in myonuclei probably stems from creatine’s ability to increase levels of the myogenic transcription factor MRF4.[58]

Research

ALS

Muscle disorders

A meta-analysis found that creatine treatment increased muscle strength in muscular dystrophies, and potentially improved functional performance.[60] Creatine treatment does not appear to improve muscle strength in people who have metabolic myopathies.[60] High doses of creatine lead to increased muscle pain and an impairment in activities of daily living when taken by people who have McArdle disease.[60]

Parkinson’s disease

Creatine’s impact on mitochondrial function has led to research on its efficacy and safety for slowing Parkinson’s disease. As of 2014, the evidence did not provide a reliable foundation for treatment decisions, due to risk of bias, small sample sizes, and the short duration of trials.[61]

References

^ abBarcelos RP, Stefanello ST, Mauriz JL, Gonzalez-Gallego J, Soares FA (2016). “Creatine and the Liver: Metabolism and Possible Interactions”. Mini Reviews in Medicinal Chemistry. 16 (1): 12–8. doi:10.2174/1389557515666150722102613. PMID26202197. The process of creatine synthesis occurs in two steps, catalyzed by L-arginine:glycine amidinotransferase (AGAT) and guanidinoacetate N-methyltransferase (GAMT), which take place mainly in kidney and liver, respectively. This molecule plays an important energy/pH buffer function in tissues, and to guarantee the maintenance of its total body pool, the lost creatine must be replaced from diet or de novo synthesis.

^ abcdeCooper R, Naclerio F, Allgrove J, Jimenez A (July 2012). “Creatine supplementation with specific view to exercise/sports performance: an update”. Journal of the International Society of Sports Nutrition. 9 (1): 33. doi:10.1186/1550-2783-9-33. PMC3407788. PMID22817979. Creatine is produced endogenously at an amount of about 1 g/d. Synthesis predominately occurs in the liver, kidneys, and to a lesser extent in the pancreas. The remainder of the creatine available to the body is obtained through the diet at about 1 g/d for an omnivorous diet. 95% of the bodies creatine stores are found in the skeletal muscle and the remaining 5% is distributed in the brain, liver, kidney, and testes [1].

^ abcdBrosnan ME, Brosnan JT (August 2016). “The role of dietary creatine”. Amino Acids. 48 (8): 1785–91. doi:10.1007/s00726-016-2188-1. PMID26874700. The daily requirement of a 70-kg male for creatine is about 2 g; up to half of this may be obtained from a typical omnivorous diet, with the remainder being synthesized in the body … More than 90% of the body’s creatine and phosphocreatine is present in muscle (Brosnan and Brosnan 2007), with some of the remainder being found in the brain (Braissant et al. 2011). … Creatine synthesized in liver must be secreted into the bloodstream by an unknown mechanism (Da Silva et al. 2014a)